1. Field of the Invention
The present invention relates to a paper shredder and component parts thereof, and more particularly, to an automatic paper feeding sensing device for a paper shredder in an optical detection or lever-type detection manner, a paper feeding device including the automatic paper feeding sensing device, and a paper shredder including the devices.
2. Description of the Related Art
Paper shredders are office machines which are used to shred confidential documents swiftly and safely. Such a paper shredder includes a paper feeding sensing device as a unit which automatically detects papers to operate a driving motor when papers to be shredded are put into the paper shredder. The paper feeding sensing device is configured to detect papers being fed and drive the driving motor. The driving motor operates a shredder cutter to shred the documents.
However, typical paper shredders adopt non-contact sensors. When such a non-contact sensor is used for an extended period of time, paper dust is likely to be heaped on the surface of the sensor, causing the sensor to malfunction even when there is no paper to be detected. In this case, the paper dust must be wiped off for the sensor and the shredder to work normally. However, it is almost impossible for an ordinary user to disassemble the paper shredder himself or herself and wipe off the dust on the surface of the sensor.
Also, when there is only one sheet of paper waiting to be shredded, the signal sent by the sensor easily penetrates the paper and causes the sensor to malfunction. It can be addressed by lowering the sensitivity of the sensor. Then, however, the failure rate of the paper shredder is prone to increase due to the malfunctioning caused by the paper dust.
A paper feeding device of a paper shredder including such a paper feeding sensing device is configured to feed papers to be shredded, sheet by sheet or sheets by sheets, into the paper shredder using the paper feeding rollers. A paper shredder including an automatic paper feeding device according to a related art has a paper feeding structure which is employed to different product lines such as printers and fax machines so as to continuously and automatically feed a certain amount of paper.
In the paper feeding method applied to the different product lines according to the related art, one end of the sheet of paper is controlled to continuously feed a certain amount of paper. When multiple sheets of paper are supplied simultaneously to the paper feeding tray or the paper tray, the topmost sheet of standby papers is transferred into a position for the next shredding process by the paper feeding roller while the rest of the sheets are held in the tray by providing a raised spot having a predetermined height.
However, the paper shredder has a purpose different from those of the different product lines such as printers and fax machines and, therefore, papers to be fed into the paper shredder are significantly deteriorated in quality. That is, printers and fax machines have to give the paper fed back after printing and facsimile processes, respectively. Also, the sheets of paper need to be read, checked and stored in most cases, which requires new paper or scratch paper whose quality and usability are not inferior to those of new paper to be employed. On the contrary, a paper shredder is configured to shred paper and the paper fed into the shredder may be crumpled or torn.
Thus, when papers much damaged or bent by such reasons as exposure to moisture for a long time are fed into the paper shredder in the above-described feeing manner for shredding, jamming, excessive feeding, and feeding failure could occur and the purpose of the paper feeding device could not be met.
Further, the paper feeding device according to the related art have paper feeding entrances with a certain limited height, causing paper jamming in many cases when bent or crumpled paper is fed through the entrances.